For more than 20 years, Alan Robert has been the bassist and primary songwriter for Life of Agony, a hard rock act that cultivated a fervent following while touring with the likes of mega acts Black Sabbath and Tool.

That career alone would be the envy of most young artists and musicians looking to make a mark. Yet the Brooklyn-born Robert, 45, hasn't limited himself to music during his time in the chaotic world of heavy metal and rock 'n' roll.

He carved out other niches for himself in other creative fields: He's written and drawn comic books and graphic novels such as "Killogy" and "Crawl to Me." Last year, he dove into the adult coloring book trend with "The Beauty of Horror." It turned out to be such a success for Robert and publisher IDW that a sequel, "The Beauty of Horror 2," is slated to go on sale Tuesday, Sept. 19. (Robert says a third volume could be coming if all goes well with part two.)

While Robert himself isn't a household name, his career is a testament to the hustle, dexterity, dedication and shrewdness that goes into a successful career in the arts. Recently Robert shared with CNBC some of the biggest professional and financial lessons he's learned over the years:

Don't quit your day job – yet

It may feel tempting to embrace the romance of the art life, but Robert cautions against that, especially if you don't have any cash socked away.

"If you are living paycheck to paycheck with no savings, you simply cannot quit and have nothing to live on," Robert said. "There is nothing wrong with working a day job while trying to pursue your dreams. I did it for many, many years."

Don't spend money like you have something to prove

There's little margin for financial error if you're trying to make your career in the arts, even when you start making more money than you're used to.

When Robert was younger, he would take a lot of expensive trips to go scuba diving in the Caribbean between tours with Life of Agony. Back then, he was making a lot less money than he makes now, but his sense of responsibility grew with age.

"I don't spend money frivolously. I'm not out to prove anything to anyone," he said. "I don't need a flashy car or stuff like that to impress people."

Diversify your skills and interests

It's not safe for someone pursuing an independent creative career to stick with one discipline or skill set. In Robert's experience, it pays off to keep pursuing learning opportunities. A few years back, for instance, he decided to scrap traditional penciling and inking for his "Killogy" comic book series and take up digital drawing.

It took some time to get used to, but he ended up saving a lot of time and money.

"I always push myself to learn new technologies and software, even if it seems like a big challenge at first because, in the long run, my range as a creative individual will grow," he explained. "I will be able to take on more types of projects."

Use your spare time wisely – and flexibly

Life can be hectic for a touring musician, but there's also a lot of downtime that comes between shows. It makes sense to capitalize on those gaps, Robert stated, particularly for an artist with a load of projects in the works.

While on the road, he's written and drawn books, worked on graphic-design projects, and written scripts. "When I'm out there, I rarely stop," he said. "I've always said that insomnia is the key to productivity."

Make your own stability

The life of a freelance artist is all about hustle, but that doesn't mean you can't enjoy a measure of stability in your life. Robert worked as a creative director at an internet company for eight years in New York City. It gave him a steady paycheck, health insurance and job security. But the commute was a "killer," and he would barely have time to see his family getting home at 8 p.m. every night.

These days, he may work more hours in the day, but he sets his own schedule and lives life on his own terms — with multiple revenue streams.

"I've found that working for myself is not only much more enjoyable and rewarding, but I also have a much better quality of life. I'm able to pick and choose the projects I work on, plus I get to take my kid to school and have dinner as a family," Robert said. "You don't get that time back. Those moments are gone forever. I've learned to cherish them a lot more now."